The present invention relates to a method of manufacturing an electronics device such as a semiconductor integrated circuit device, a superconductive device, a micromachine, a TFT (Thin Film Transistor), a circuit board and the like, and in particular to a technique effectively applied to a lithographic technique in a method step of manufacturing a semiconductor integrated circuit device.
In the method step of manufacturing a semiconductor integrated circuit device, a lithographic technique is used as a method of transferring a fine pattern onto a semiconductor wafer. In the lithographic technique, a projection exposure device is mainly used, and a pattern in a photo mask mounted to the projection exposure device is transferred onto the semiconductor wafer, whereby a device pattern thereon is formed.
Usually, the photo mask is produced by processing a light shielding material such as chromium (Cr) or the like formed on a transparent quartz substrate. That is, the photo mask is constituted by forming a light shielding film of chromium etc. in a desired shape on a quartz substrate.
The processing of the light shielding film is for example as follows: That is, an electron-beam resist is applied onto a light shielding film, and then a desired pattern is drafted on the electron-beam resist by an electron beam drafting device. Subsequently, a resist pattern with a desired shape is formed by development, and then the light shielding film is processed by dry etching or wet etching using the resist pattern as a mask. Thereafter, the resist is removed, and washing or the like of the light shielding film is performed to form a light-shielding pattern having a desired shape on the quartz substrate.
Besides the ordinary photo mask in which the light shielding film made of chromium, etc. is formed in a desired shape as described above, various mask structures for the purpose of improving resolution in lithography have been proposed in recent years. For example, in Japanese Patent Laid-open No. 4-136854, a translucent film is formed on a light shielding portion in a photo mask, and the phase of slight light passing through the translucent film and that of light passing through the transparent pattern are made inverse to each other. That is, the intensity of the light passing through the translucent film is quite low to expose the photoresist, and the phase of this light and that of light passing through the transparent pattern are made inverse to each other. The phase of light passing through the translucent film is made inverse to that of light passing through the transparent pattern used as a main pattern, and thus the intensity of light in the boundary between the transparent pattern and the translucent film approaches 0 (zero). As a result, the ratio of the intensity of light passing through the transparent pattern to that of light passing through the boundary is made relatively high, so that it is possible to obtain a light intensity distribution having high contrast in comparison with the ordinary photo mask using no translucent film.
The photo mask described in the above-mentioned reference is called an attenuation type phase-shift mask. This attenuation type phase-shift mask is obtained by replacing a light shielding film made of chromium etc. with an attenuation type phase-shift film, and is produced by almost the same steps as the steps of manufacturing the ordinary photo mask.
Further, there is an exposure method called super resolution capable of resolving much finer patterns than that of the wavelength of exposure light. The most effective method of forming the finer patterns among the super resolution is called an alternation type phase shifting exposure method. This alternation type phase shifting exposure method is a method of: forming a structure called phase shifters in which light shielding portions are put between respective exposure light transmission portions of the ordinary photo mask, namely, between respective window portions to which a quartz substrate is exposed, whereby phases of exposure light are made alternately inverse; and performing the light exposing with the structure. According to this light exposure method, the phase of light passing through the ordinary transmission portions and the phase of light penetrating the phase shifter are made inverse to each other, so that there occurs a region where the amplitude of light is 0 in the light shielding portions therebetween. When the amplitude becomes 0, the intensity of light also becomes 0. So, the resolution is significantly improved and the cycle between the light shielding portions and the phase shifters alternately arranged can be resolved to nearly ½ of the wavelength of exposure light. The photo mask having such light shielding portions and phase shifters is called an alternation type phase shift mask.
Involving higher accuracy and diversification of semiconductor integrated circuit devices, the ordinary photo mask used in the lithography technique requires severer processing accuracy. The phase shift mask having the special structure described above is also required. Therefore, generally, the production costs of about 20 to 40 photo masks prepared in manufacturing one kind of semiconductor integrated circuit device have been significantly higher, and the time required for production of such photo masks has been also increased.
Japanese Patent Laid-open No. 5-289307 discloses a method in which a light shielding film in a photo mask is formed from a radiation sensitive resist film such as a photoresist film in place of a conventional metal film such as Cr or the like. This method makes use of the properties of a benzene nucleus that is a major component of the ordinary electron-beam resist film or a light-sensitive resist film, the properties being that the benzene nucleus has an extremely high photo absorption band at the wavelength (about 193 nm) of an ArF (argon fluoride) excimer laser light source. Accordingly, this method does not require the step of etching a light shielding film or the step of removing a photoresist film, thereby enabling reduction in production costs of the photo masks, improvement in dimensional accuracy and reduction in defects.